1. Field of the Invention
The present invention relates to message transmitting systems for missiles, for example, and more particularly to a message receiving device which may be mounted on the missile itself.
2. Description of the Prior Art
Such systems usually have a function either of remote neutralization or of trajectory calculation. Remote control orders are for example transmitted from a ground station to the missile. An order receiving device mounted on the misile allows these messages to be received and decoded.
These messages may therefore for example have a remote control function or else a maintain function (M) or else a dead-man function (HM) or else an anti-jamming function. These different messages, digital or analog, are well known to a man skilled in the art and will not be further described.
In the case of messages transmitted for example by coded pulses, a sequence S.sub.i is a group of several pulses, for example two, the first being the reference pulse and the second being transmitted a time .DELTA.t.sub.i later, .DELTA.t.sub.i depending on the rank of the sequence.
A word is an assembly of several sequences, for example seven.
An order is formed by an assembly of identical words; for an order to be executed, a number of words defined beforehand must be correctly received.
A code is an assembly of several words, for example seven, allowing for example seven missiles to be destroyed separately.
The object of the present invention is to receive these different words of the code and recognize them.
Known devices usually comprise a time counter whose initialization is effected by reception of the first pulse of a sequence. Such known systems are therefore unreliable. In fact, as soon as the time counter has been initialized, it can no longer count any other time interval. These known systems are therefore very sensitive to disturbances, for if the time counter has been initialized by an erroneous pulse, the receiving system is no longer capable of recognizing other pulse groups.
The invention proposes overcoming these defects of known systems and provides a message receiving system, with correlation, using a digital delay line.